The present invention relates generally to pumps and pertains particularly to extrusion pumps.
Slurries of concrete, plaster and similar materials are difficult to pump with conventional impeller pumps. Such materials are typically handled by an extrusion pump, generally referred to as a Moineau pump, which includes a rigid cylinder or cylindrical housing in which is mounted an elastomeric pump stator in an unstressed condition. The stator includes a spiral interior bore corresponding to the external shape of an elongated spiral shaped rotor or impeller, which passes through the cylinder. The rotor is preferably formed of steel or the like, and upon rotation deforms the interior of the stator, so achieving a pumping action. Such pumps in accordance with the prior art are shown in U.S. Pat. No. 3,006,615 issued Oct. 21, 1961 to W. R. Mason, Jr., and U.S. Pat. No. 3,093,364 issued June 11, 1963 to Schoonover.
Such pumps have been, and are extensively used in the construction industry today. One drawback to such pumps is that the bore of the stator wears at a rapid rate requiring replacement quite frequently. Because of the structure this also requires, replacement of the housing of the pump section which as previously described generally comprises a cylindrical housing formed of a section of pipe on the order of three to four inches in diameter in which the elastomeric stator is molded. The frequent and continuous replacement of this unit becomes quite expensive over a period of time.
Another drawback to such prior art devices is the fact that as the stator bore wears the pressure of the pump begins to drop. Thus, a new pump stator assembly begins at optimum pressure with the pressure dropping off to a substantially unworkable pressure at the end of the life of the stator.
It is therefore desirable that means be available which reduces the cost of replacement of such pump units and reduces the pressure loss during its lifetime.